/*
 * Copyright 2013 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.app.view_controller;

import android.animation.Animator;
import android.animation.AnimatorListenerAdapter;
import android.animation.ValueAnimator;
import android.graphics.Rect;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.widget.AbsListView;
import android.widget.ListView;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

/**
 * A {@link android.view.View.OnTouchListener} that makes the list items in a
 * {@link ListView} dismissable. {@link ListView} is given special treatment
 * because by default it handles touches
 * for its list items... i.e. it's in charge of drawing the pressed state (the
 * list selector),
 * handling list item clicks, etc.
 * 
 * <p>
 * After creating the listener, the caller should also call
 * {@link ListView#setOnScrollListener(android.widget.AbsListView.OnScrollListener)}
 * , passing in the scroll listener returned by {@link #makeScrollListener()}.
 * If a scroll listener is already assigned, the caller should still pass scroll
 * changes through to this listener. This will ensure that this
 * {@link SwipeDismissListViewTouchListener} is paused during list view
 * scrolling.
 * </p>
 * 
 * <p>
 * Example usage:
 * </p>
 * 
 * <pre>
 * SwipeDismissListViewTouchListener touchListener = new SwipeDismissListViewTouchListener(listView,
 * 		new SwipeDismissListViewTouchListener.OnDismissCallback() {
 * 			public void onDismiss(ListView listView, int[] reverseSortedPositions) {
 * 				for (int position : reverseSortedPositions) {
 * 					adapter.remove(adapter.getItem(position));
 * 				}
 * 				adapter.notifyDataSetChanged();
 * 			}
 * 		});
 * listView.setOnTouchListener(touchListener);
 * listView.setOnScrollListener(touchListener.makeScrollListener());
 * </pre>
 * 
 * <p>
 * This class Requires API level 12 or later due to use of
 * {@link android.view.ViewPropertyAnimator}.
 * </p>
 */
public class SwipeDismissListViewTouchListener implements View.OnTouchListener {
	// Cached ViewConfiguration and system-wide constant values
	private int mSlop;
	private int mMinFlingVelocity;
	private int mMaxFlingVelocity;
	private long mAnimationTime;

	// Fixed properties
	private ListView mListView;
	private DismissCallbacks mCallbacks;
	private int mViewWidth = 1; // 1 and not 0 to prevent dividing by zero

	// Transient properties
	private List<PendingDismissData> mPendingDismisses = new ArrayList<PendingDismissData>();
	private int mDismissAnimationRefCount = 0;
	private float mDownX;
	private boolean mSwiping;
	private VelocityTracker mVelocityTracker;
	private int mDownPosition;
	private View mDownView;
	private boolean mPaused;

	/**
	 * The callback interface used by {@link SwipeDismissListViewTouchListener}
	 * to inform its client
	 * about a successful dismissal of one or more list item positions.
	 */
	public interface DismissCallbacks {
		/**
		 * Called to determine whether the given position can be dismissed.
		 */
		boolean canDismiss(int position);

		/**
		 * Called when the user has indicated they she would like to dismiss one
		 * or more list item
		 * positions.
		 * 
		 * @param listView
		 *            The originating {@link ListView}.
		 * @param reverseSortedPositions
		 *            An array of positions to dismiss, sorted in descending
		 *            order for convenience.
		 */
		void onDismiss(ListView listView, int[] reverseSortedPositions);
	}

	/**
	 * Constructs a new swipe-to-dismiss touch listener for the given list view.
	 * 
	 * @param listView
	 *            The list view whose items should be dismissable.
	 * @param callbacks
	 *            The callback to trigger when the user has indicated that she
	 *            would like to
	 *            dismiss one or more list items.
	 */
	public SwipeDismissListViewTouchListener(ListView listView, DismissCallbacks callbacks) {
		ViewConfiguration vc = ViewConfiguration.get(listView.getContext());
		mSlop = vc.getScaledTouchSlop();
		mMinFlingVelocity = vc.getScaledMinimumFlingVelocity() * 16;
		mMaxFlingVelocity = vc.getScaledMaximumFlingVelocity();
		mAnimationTime = listView.getContext().getResources().getInteger(android.R.integer.config_shortAnimTime);
		mListView = listView;
		mCallbacks = callbacks;
	}

	/**
	 * Enables or disables (pauses or resumes) watching for swipe-to-dismiss
	 * gestures.
	 * 
	 * @param enabled
	 *            Whether or not to watch for gestures.
	 */
	public void setEnabled(boolean enabled) {
		mPaused = !enabled;
	}

	/**
	 * Returns an {@link android.widget.AbsListView.OnScrollListener} to be
	 * added to the {@link ListView} using
	 * {@link ListView#setOnScrollListener(android.widget.AbsListView.OnScrollListener)}
	 * .
	 * If a scroll listener is already assigned, the caller should still pass
	 * scroll changes through
	 * to this listener. This will ensure that this
	 * {@link SwipeDismissListViewTouchListener} is
	 * paused during list view scrolling.</p>
	 * 
	 * @see SwipeDismissListViewTouchListener
	 */
	public AbsListView.OnScrollListener makeScrollListener() {
		return new AbsListView.OnScrollListener() {
			@Override
			public void onScrollStateChanged(AbsListView absListView, int scrollState) {
				setEnabled(scrollState != AbsListView.OnScrollListener.SCROLL_STATE_TOUCH_SCROLL);
			}

			@Override
			public void onScroll(AbsListView absListView, int i, int i1, int i2) {
			}
		};
	}

	/**
	 * Manually cause the item at the given position to be dismissed (trigger
	 * the dismiss
	 * animation).
	 */
	public void dismiss(int position) {
		dismiss(getViewForPosition(position), position, true);
	}

	@Override
	public boolean onTouch(View view, MotionEvent motionEvent) {
		if (mViewWidth < 2) {
			mViewWidth = mListView.getWidth();
		}

		switch (motionEvent.getActionMasked()) {
		case MotionEvent.ACTION_DOWN: {
			if (mPaused) {
				return false;
			}

			// TODO: ensure this is a finger, and set a flag

			// Find the child view that was touched (perform a hit test)
			Rect rect = new Rect();
			int childCount = mListView.getChildCount();
			int[] listViewCoords = new int[2];
			mListView.getLocationOnScreen(listViewCoords);
			int x = (int) motionEvent.getRawX() - listViewCoords[0];
			int y = (int) motionEvent.getRawY() - listViewCoords[1];
			View child;
			for (int i = 0; i < childCount; i++) {
				child = mListView.getChildAt(i);
				child.getHitRect(rect);
				if (rect.contains(x, y)) {
					mDownView = child;
					break;
				}
			}

			if (mDownView != null) {
				mDownX = motionEvent.getRawX();
				mDownPosition = mListView.getPositionForView(mDownView);
				if (mCallbacks.canDismiss(mDownPosition)) {
					mVelocityTracker = VelocityTracker.obtain();
					mVelocityTracker.addMovement(motionEvent);
				} else {
					mDownView = null;
				}
			}
			//view.onTouchEvent(motionEvent);
			return true;
		}

		case MotionEvent.ACTION_UP: {
			if (mVelocityTracker == null) {
				//view.onTouchEvent(motionEvent);
				break;
			}

			float deltaX = motionEvent.getRawX() - mDownX;
			mVelocityTracker.addMovement(motionEvent);
			mVelocityTracker.computeCurrentVelocity(1000);
			float velocityX = mVelocityTracker.getXVelocity();
			float absVelocityX = Math.abs(velocityX);
			float absVelocityY = Math.abs(mVelocityTracker.getYVelocity());
			boolean dismiss = false;
			boolean dismissRight = false;
			if (Math.abs(deltaX) > mViewWidth / 2) {
				dismiss = true;
				dismissRight = deltaX > 0;
			} else if (mMinFlingVelocity <= absVelocityX && absVelocityX <= mMaxFlingVelocity
					&& absVelocityY < absVelocityX) {
				// dismiss only if flinging in the same direction as dragging
				dismiss = (velocityX < 0) == (deltaX < 0);
				dismissRight = mVelocityTracker.getXVelocity() > 0;
			}
			if (dismiss) {
				// dismiss
				dismiss(mDownView, mDownPosition, dismissRight);
			} else {
				// cancel
				mDownView.animate().translationX(0).alpha(1).setDuration(mAnimationTime).setListener(null);
			}
			mVelocityTracker.recycle();
			mVelocityTracker = null;
			mDownX = 0;
			mDownView = null;
			mDownPosition = ListView.INVALID_POSITION;
			mSwiping = false;
			break;
		}

		case MotionEvent.ACTION_CANCEL: {
			if (mVelocityTracker == null) {
				break;
			}

			if (mDownView != null) {
				// cancel
				mDownView.animate().translationX(0).alpha(1).setDuration(mAnimationTime).setListener(null);
			}
			mVelocityTracker.recycle();
			mVelocityTracker = null;
			mDownX = 0;
			mDownView = null;
			mDownPosition = ListView.INVALID_POSITION;
			mSwiping = false;
			break;
		}

		case MotionEvent.ACTION_MOVE: {
			if (mVelocityTracker == null || mPaused) {
				break;
			}

			mVelocityTracker.addMovement(motionEvent);
			float deltaX = motionEvent.getRawX() - mDownX;
			if (Math.abs(deltaX) > mSlop) {
				mSwiping = true;
				mListView.requestDisallowInterceptTouchEvent(true);

				// Cancel ListView's touch (un-highlighting the item)
				MotionEvent cancelEvent = MotionEvent.obtain(motionEvent);
				cancelEvent.setAction(MotionEvent.ACTION_CANCEL
						| (motionEvent.getActionIndex() << MotionEvent.ACTION_POINTER_INDEX_SHIFT));
				mListView.onTouchEvent(cancelEvent);
				cancelEvent.recycle();
			}

			if (mSwiping) {
				mDownView.setTranslationX(deltaX);
				mDownView.setAlpha(Math.max(0.15f, Math.min(1f, 1f - 2f * Math.abs(deltaX) / mViewWidth)));
				return true;
			}
			break;
		}
		}
		return false;
	}

	private void dismiss(final View view, final int position, boolean dismissRight) {
		++mDismissAnimationRefCount;
		if (view == null) {
			// No view, shortcut to calling onDismiss to let it deal with adapter
			// updates and all that.
			mCallbacks.onDismiss(mListView, new int[] { position });
			return;
		}

		view.animate().translationX(dismissRight ? mViewWidth : -mViewWidth).alpha(0).setDuration(mAnimationTime)
				.setListener(new AnimatorListenerAdapter() {
					@Override
					public void onAnimationEnd(Animator animation) {
						performDismiss(view, position);
					}
				});
	}

	private View getViewForPosition(int position) {
		int index = position - (mListView.getFirstVisiblePosition() - mListView.getHeaderViewsCount());
		return (index >= 0 && index < mListView.getChildCount()) ? mListView.getChildAt(index) : null;
	}

	class PendingDismissData implements Comparable<PendingDismissData> {
		public int position;
		public View view;

		public PendingDismissData(int position, View view) {
			this.position = position;
			this.view = view;
		}

		@Override
		public int compareTo(PendingDismissData other) {
			// Sort by descending position
			return other.position - position;
		}
	}

	private void performDismiss(final View dismissView, final int dismissPosition) {
		// Animate the dismissed list item to zero-height and fire the dismiss callback when
		// all dismissed list item animations have completed. This triggers layout on each animation
		// frame; in the future we may want to do something smarter and more performant.

		final ViewGroup.LayoutParams lp = dismissView.getLayoutParams();
		final int originalHeight = dismissView.getHeight();

		ValueAnimator animator = ValueAnimator.ofInt(originalHeight, 1).setDuration(mAnimationTime);

		animator.addListener(new AnimatorListenerAdapter() {
			@Override
			public void onAnimationEnd(Animator animation) {
				--mDismissAnimationRefCount;
				if (mDismissAnimationRefCount == 0) {
					// No active animations, process all pending dismisses.
					// Sort by descending position
					Collections.sort(mPendingDismisses);

					int[] dismissPositions = new int[mPendingDismisses.size()];
					for (int i = mPendingDismisses.size() - 1; i >= 0; i--) {
						dismissPositions[i] = mPendingDismisses.get(i).position;
					}
					mCallbacks.onDismiss(mListView, dismissPositions);

					ViewGroup.LayoutParams lp;
					for (PendingDismissData pendingDismiss : mPendingDismisses) {
						// Reset view presentation
						pendingDismiss.view.setAlpha(1f);
						pendingDismiss.view.setTranslationX(0);
						lp = pendingDismiss.view.getLayoutParams();
						lp.height = originalHeight;
						pendingDismiss.view.setLayoutParams(lp);
					}

					mPendingDismisses.clear();
				}
			}
		});

		animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
			@Override
			public void onAnimationUpdate(ValueAnimator valueAnimator) {
				lp.height = (Integer) valueAnimator.getAnimatedValue();
				dismissView.setLayoutParams(lp);
			}
		});

		mPendingDismisses.add(new PendingDismissData(dismissPosition, dismissView));
		animator.start();
	}
}